Could you please tell me how to verify the Premultiplied Alpha setting is consistent in both the export from the Spine editor and the runtime configuration ?

Nate thank you for the solution.. I've applied the same wrt the used animations.

The artist has set the PMA to false, so from the code i've also set it to false. Now this resolved the issue which i faced earlier ( the image attached with the original question ).

But somehow, when i use another set of animations, with same settings and same version of Spine, i still see some mismatch in the web player.

With this description, i've attached a snippet of the code and another image where i'm seeing the issue. Please if you could help me with this, i'd be very much thankful to you! Lemme know if you need any more input from me.

@Misaki here's the issue that i raised earlier.

Misaki sure..

document.getElementById("uploadForm").addEventListener("submit", async function (e) {
e.preventDefault();

const formData = new FormData(this);

const res = await fetch("/uploads", {
    method: "POST",
    body: formData
});

const data = await res.json();

const jsonFiles = data.files.filter(f => f.originalname.endsWith(".json"));
const atlasFiles = data.files.filter(f => f.originalname.endsWith(".atlas"));
const imageFiles = data.files.filter(f => f.originalname.endsWith(".webp") || f.originalname.endsWith(".png") || f.originalname.endsWith(".jpg"));

if (jsonFiles.length !== 1) {
    alert("Please upload the JSON file.");
    return;
}

if (atlasFiles.length !== 1) {
alert("Please upload the ATLAS file.");
return;
}

if (imageFiles.length < 1) {
    alert("Please upload image files (WEBP, PNG, or JPG).");
    return;
}

const jsonUrl = `/uploads/${jsonFiles[0].originalname}`;
const atlasUrl = `/uploads/${atlasFiles[0].originalname}`;

document.getElementById("player-container").innerHTML = "";

new spine.SpinePlayer("player-container", {
    jsonUrl: jsonUrl,
    atlasUrl: atlasUrl,
    showControls: true,
    backgroundColor: "#eeeeee",
    alpha: false,
    preserveDrawingBuffer: true,
    autoplay: true,
    loop: false,
    scale: 1,
    premultipliedAlpha: false
});

});

here is the actual code i'm using for my project. I'm taking input files from user and playing the spine animations in the Spine Web Player.
But for some specific animations, i'm seeing the blur and distorted animations in the web player.

I've attached the exact part of the previous image that i uploaded, where you can see a white square block which is supposed to be hidden.

Davide sure !!
i'll definitely try this way too! Thanks..

Misaki
it looks like the issue is mostly related with the PMA. The assets i'm using or i'll be using, will not always have the PMA enabled and i don't think i can change the premultipliedAlpha dynamically for each time. I'll still try to investigate on my end thru the texture packer settings. And will see if it results in a clean viewing of the Animations.

By the blurred or distorted part, i want to say that some extra elements, probably the borders or some animation effects, are visible on the screen ( the white square box visible in the last added image ).

It is working correctly for some other spines, but some spines are showing unwanted elements on the web player. Will see what i can do from the texture packer settings.

Thank you again for all the support!! I appreciate it!